As water-soluble cellulose ether such as hydroxyalkyl cellulose exhibits hydrophilicity and thickening properties, it is widely used in a variety of fields such as those pertaining to thickening agents, adhesives, dispersants, and emulsion stabilizers. In these applications, as water-soluble cellulose ether is generally dissolved for use in water or a mixed solvent containing water (hereinafter referred to as “aqueous solvent”), it is ordinarily used in microparticle form for reasons of solubility.
However, as this microparticle-type of water-soluble cellulose ether has very high solubility in water or aqueous solvent, when introduced without alteration into water or aqueous solvent, only the surface of each particle moistens with water and dissolves, and neighboring particles bond into agglomerations, producing so-called undissolved powder lumps. Once these gel clumps are produced, the contact area of the water-soluble cellulose ether and the water is greatly reduced, and it takes time for the water-soluble cellulose ether to completely dissolve, which is a problem in terms of industrial process.
To counter this type of problem, glyoxal treatment is known where the water-soluble cellulose ether is treated with glyoxal to raise hydrophobicity and enhance aqueous dispersibility. According to glyoxal treatment, glyoxal reacts with hydroxyl groups of water-soluble cellulose ether, resulting in crosslinkage of the glyoxal and the water-soluble cellulose ether due to hemiacetal bonding. As this crosslinkage hydrolyzes due to alkali and heat, water-soluble cellulose ether that has undergone glyoxal treatment disperses with excellent aqueous dispersibility when introduced into water or aqueous solvent, and subsequently manifests excellent solubility due to alkali and heat.
With respect to glyoxal treatment, however, there is demand for alternative techniques, because glyoxal has been designated as a mutagenic substance.
As alternative techniques to glyoxal treatment, silane modification methods which use silane compounds have been proposed. As silane modification methods, for example, there have been proposals of methods which use amino silane and epoxy silane (Patent Documents 1, 2), methods which use alkyltrialkoxyl silane, alkyltetraacyloxy silane, tetraalkoxy silane, and tetraacyloxy silane (Patent Documents 3-6), and so on.
On the other hand, production of cationized cellulose by cationization of water-soluble cellulose ether is being conducted. As a method of producing cationized cellulose, there is known to be a method which causes water-soluble cellulose ether to react with a cationizing agent in the presence of alkali (Patent Document 7). The aforementioned cationized cellulose is widely used, primarily as a conditioning agent for shampoos and body soaps.
Patent Document 1: Japanese Examined Patent Application, Second Publication No. S51-2103
Patent Document 2: Japanese Unexamined Patent Application, First Publication No. S47-35073
Patent Document 3: Japanese Examined Patent Application, Second Publication No. H6-39481
Patent Document 4: Japanese Unexamined Patent Application, First Publication No. H8-183801
Patent Document 5: Japanese Laid-Open Patent Application No. 2004-155805
Patent Document 6: Japanese Unexamined Patent Application, First Publication No. S61-195138
Patent Document 7: Japanese Laid-Open Patent Application No. 2005-171089